Crimping fibers



Dec. 22, 1959 T. c. SPENCE ETAL 2,917,784

CRIMPING FIBERS Filed June 5, 1957 s Sheets-Sheet 1 IN V EN TORS. Thomas 6. Spence BY Rober/5. Funk HTTOR/VEKS' Dec. 22, 1959 -r. c. SPENCE ETAL 2,917,784

CRIMPING FIBERS Filed June 5, 1957 3 Sheets-Sheet 2 HTTOR/VEYS Dec. 22, 1959 T. c. sPENcE ETAL 2,917,784

CRIMPING FIBERS Filed June 5, 1957 3 Sheets-Sheet 3 IN V EN TORS. 7homas 6. Spence Rober/ 5. Funk HTTORNEYS C Fl ENG FIBERS Application June 5, H57, Serial No. 663,764

12 Claims. (Cl. 19--66) The present invention contributes to the textile art. It has reference to the crimping of fibers, filaments and the like or related shaped articles and forms that may be of natural, artificial or synthetic origin. More particularly, this invention relates to improved mechanical means, of the stufiing-box type or variety of apparatus, for crimping fibers mid to the processing of fibers therewith.

For many yarn and fabric constructions and other textile use applications, it is of great benefit to crimp various fibers and filaments that, without physical modification, would retain a normally straight and undistorted strandular configuration or, at best, would have a relatively slight pattern of undulation. The common desideration in quest is to thereby impart to the fibers a crimp, crinkle, curliness or waviness which simulates and resembles that associated with and inherently obtained in the better grades and higher qualities of fine wool. Ordinarily, the greatest necessity for crimping is found to exist in the man-made artificial and synthetic fibers. It is not unknown, however, to provide or improve crimp in many natural fibers. Thus, for example, inferior or less desirable species of wool and other proteinous natural fibers may frequently be upgraded by being mechanically crimped to a greater than inherent degree.

Mechanical crimpers of the stufiing-box variety are well known and have been Widely employed for the indicated purpose. The art is familiar with many diverse and particularized embodiments of such crimping apparatus and is cognizant of their application in textile processes. In general, stufiing-box crimpers operate by forcing a tow bundle or like closely associate plurality of fibers into a crimping zone or chamber that is contained within and confined by a stufiing-box having a. restrictive outlet or other resistive effect on the passage of the fibers being forced therethrough. Various conveying means, comprised predominantly of opposed, cooperating feed rollers that grip or form a bight upon the tow bundle being handled, may be employed for forwarding the fibers into the stufiing-box wherein, under the combined effect of the forwarding feed rolls and the plenum of the crimping zone, they pack within the stuffing-box in a more or less zig'zag or accordion-folded column. The influences at play under such conditions cause the fibers to assume a greater or lesser crimp pattern which results from the physical distortion that is imposed upon them during their passage through the stuffing box, especially upon their introduction therein.

It is not uncommon in the utilization of such apparatus to plastify the fibers during (or prior to) their passage through and residence in the stufiing-box. Dry heat, steam and various solvents and swelling agents may be employed in order to accomplish this. The plastification of the fibers serves to diminish their natural resilience and render them more amenable to accepting the crimp that is imposed upon their introduction to and while they are being held under distortion in the stufiing-box. Likewise, certain synthetic fibers, particularly acrylonitrile polymer fibers, may be crimped while they are in an aquagel condition before they have been dried and transformed to a permanent, hydrophobic physical form. The hydrated or water-swollen aquagel fibers are usually obtained by extruding a spinning solution of the fiber-form* ing polymer into an aqueous coagulating bath wherein the spinning solvent in the extruded filamentarystructure is replaced with water. Acrylonitrile polymer aquagels usually contain at least as much water, gravimetrically speaking, as polymer. Aquagel fibers are usually quite soft, tender and delicate. Obviously, they may be damaged easily. Most highly plastified fibers, besides those in aquagel form, are also more susceptible to physical damage than when they are in their normal state. And, even with fibers in their normally occurring structure and ordinarily existing condition, there are limits to the physical abuse that can be withstood.

In any physical deforming crimp-inducing apparatus, the potential that exists for physically damaging the fibers is dependent upon and proportional to both the force that is exerted uponthe fibers and the period of time during which the fibers are exposed to such force. In most of the conventional crimping apparatus, a high force is present for a long time. Thus, one difiiculty that exists for such reasons with many of the types of stufling-box crimpers that are available is that, literally expressed, they are too roug on the fibers. This is particularly the case when they are being employed inthe manufacture of finely crimped products such as those in the much demanded range of from, say, five totwelve or more crimps per linear inch. The situation is bad enough when normally strong, dry fiber forms are being crimped. It is worse, and frequently quite serious, when the fibers are being crimped in one or another abnormally plastified form. And, as may well be appreciated, it is generally intolerable when the conventional stufling-box crimpers are employed on aquagel fibers, particularly those that have been derived from acrylonitrile polymers.

Besides, or perhaps in connection with or synergistic to their physical severity on fibers, the conventional stuffing box type of crimping operation oftentimes turn out undesirably non-uniform products. Thus, the material that has been processed through many of the heretoforeavailable types of stuifing-box crimping appartus may frequently exhibit cycles of too few or too many, or both, crimps per inch to meet the necessary specifications. Another disadvantage, among others, of the conventional contrivances is their all too usual tendency to jam in operation. This characteristic is ordinarily aggravated when aquagel fibers, especially acrylonitrile polymer aquagels, are being crimped. In addition to being vexatious and extraordinarily damaging to fibers, the jamming of crimpers works havoc with production schedules since the apparatus is thus repeatedly kept from performing in the most desirable manner and with an economically high rate of throughput.

It would be advantageous, and it is the principal object of the invention, to provide an improved and vastly ameliorated variety of stufiing-box crimper. A particular object of the invention is to provide apparatus of the indicated variety that would be adapted to crimp and handle fibers in any of the physical forms in which they may be subjected to such process without causing damage or physical harm to the product. Yet another object is to furnish a stuffing-box crimper that would be capable of gently handling fibers even when exceedingly fine crimped products are being manufactured. A ,further object of the invention is to make a crimping device of the mentioned type available to the art that possibilitatd the preparation of crimped fiber products having utmost and non-varying uniformity. Still another object is to provide a stuffing-box crimper having little, if any,

tendency to jam'in ope ration. An additional and predominating object of the invention, more specific in nature but of great advantage, is to provide a stufiingbox crimper that would be eminently Well suited for the optimum processing of'acrylonitrile polymer aquagel' and ments and crimped in a stufiing-box crimper that is providedwith a stuffing-box of substantially rectangular cross section so designed that its interior width dimension which is parallel to the thickness of the fiat tow is between about one and two times the value:

wherein N is the pitch or number of crimps per linear, unextended inch or other unit of linear measure of finished, dried producLT-I is the thickness in inches or other consistent units of the ribbon-like tow bundle and A is a shrinkage factor that is based upon the anticipated percentage-wise reduction in the length of the fiber that is being crimped due to shrinkage upon drying or from other operations subsequent to crimping that lead to the final product. In the specific case of acrylonitrile polymer aquagel fibers, A may be taken as the shrinkage factor involved in converting the hydrated fiber that is crimped to a dry fiber form. For such instances, the value of the symbol may be found according to the following expression:

A Shrinkage factor Aquagel LengthDry Fiber Length Aquagel Length Shrinkage factors for other fibers can be similarly determined. Crimpers in accordance with the invention are highly eflicient and effective devices that are physically gentle upon the fibers being processed. The combination of crimping inducing force and deformation imposing time are both accurately and advantageously controlled so that the fiber damaging potential is desirably low due to the possible use of relatively low forces for relatively short time periods. The crimpers of the invention do not tend to jam, even when finely crimped products are being manufactured. Furthermore, they nicely fulfill the demands and requirements that are involved in and for the crimping of acrylonitrile polymer aquagel fibers and the like, as well as with fibers that are crimped while in an abnormally plastified condition.

Further features of the invention, as well as other of its objects, purposes, advantages and benefits, will be manifest in the following description and specification, taken in conjunction with the accompanying drawing that illustrates several of the many possible embodiments of the invention and in which, in so far as may be possible, like reference numerals and symbols refer to like parts, wherein:

Figure 1, a schematic perspective representation cut away partly in section, illustrates a crimping apparatus according tothe invention operating to process a suitable tow of fibers;

Figure 2 indicates the cross-sectional dimensions of the stufiing-box of a crimper designed in accordance with the invention; a

Figure 3 depicts a suitable multiple filament tow bundle for use in and with various embodiments of the invention, in which the dimensional proportions of the iii Cir

. 4 7 individual fibers have been distorted for purposes of clarity;

Figure 4 represents an individual crimped fiber product; and

Figures 5 through 13, inclusive, are representative showings of various modifications of apparatus according to the invention including, in certain of the views, advantageous design characteristics peculiar thereto.

With initial reference to the first four figures of the drawing, there is perspectively and schematically shown in Figure l a fanciful representation of a stufiingbox crimper, embodied in accordance with the invention and indicated generally by the numeral 15, operating (in a fashion that is similar to the known manner for such appliances) on a flat, ribbon-like, multiple-filament tow T'of fibers and discharging a crimped fiber product in the processed tow K. The tow T is flatly engaged by and in the bight or nip between an opposite pair of smooth faced, cooperating feed rolls, 17 and 18, that are urged one against the other in the typical fashion while being rotated in opposite directions (as indicated by the directional arrows), to force the tow into the crimping zone of the crimper. This zone is defined by the rectangular stuffing-box B having means for forming front and rear walls 20 and 21, respectively and left and right side walls 22 and 23, respectively. The front wall 2t has been partially cut away to show the tightly packed column P of the tow that has been forced into the stufling box B by the feed rolls 17 and 18 and is folded over upon itself in a zig zag fashion due to the restraining effect of the stufiing-box. The cut away front wall also exposes an advantageous means for restricting the passage of the accordion-folded, packed column of tow P in the stuffing box of the crimper. This means is in the form of a moveable restraining gate or flapper plate or gate G that depends pivotally from and is affixed by a hinge pin 32, or equivalently, to the side wall 22. The gate G is pressed laterally against the flat side of the packed column of tow P in the stuffing-box to secure the desired restriction. A pneumatic cylinder 35, operating in the direction illustrated through the rod 34, may be employed for loading the gate G against the packed column of tow P, as may spring loading or other means (not shown). Of course, a similar restraining gate may also be employed in the front or rear wall of the stufiing-box, as is hereinafter illustrated, or an end closing mechanical valve, which might be more in the form of a trap door, may also be employed.

Advantageously, both of the feed rolls 17 and 18 are positively driven at any desired rate by any means (not shown) suitable for the purpose. In some instances, however, it may be satisfactory for one of the feed rolls to be an idler. At least one of the rolls should also be pivotally mounted or laterally yieldable to better accommodate varying thicknesses, dimensional imperfections, slugs, chips and the like in the tow without causing great damage to the fibers. Feed roll 18 is indicated by the bidirectional arrow to be so mounted. Any conventional means (not shown), that usually advantageously involves spring, pneumatic or the like loading to secure uniformity, may be employed for so mounting one or both of the feed rolls 1? and 18. A stop (not shown) should also be provided on the yieldable feed roll so that the bight clearance can be accurately fixed and the roll prevented from physical impingement with the side wall. Such contact is undesirable, of course, since it may gall or damage the roll or the side wall, or both. In addition, the front wall or face plate 20 should be removably mounted in the assembly to facilitate threading or lacing up of the crimper and to permit adjustment in the width dimensions of the stufiing-box. This may be accomplished by hinging it in the assembly in a known manner (not shown) or by fastening with a belt (or bolts) 55 and washer (or washers) 56 tapped into the assembly through an opening in the face plate.

The side walls 22, 23 are also adjustably mounted on the rear wall 21 to permit dimensional changes to be made in the width of the stoning-box B. Thus, the side walls may be held in the assembly by nuts 3tl set in countersunk apertures 29 in the -walls and threaded on studs 28 extending through the apertures from the rear wall 21. The apertures may be oversize elliptical spaces or otherwise offset borings which permit movement of the side walls on the rear wall. Suitable equivalent means may also be employed. The upper portions of the side walls 22, 23 are arcuately (or otherwise) tapered in conformity with the feed rolls l7, 18 under which they are positioned. The upper and inner edges of the side walls terminate in angular deflecting shoulders 25, 26 which are closely set to the feed rolls 17 and 13, respectively, and assist in directing the tow T away from the feed rolls as it is being forced into the packed column P. Generally, the front and rear walls extend sufliciently upwardly to cover at least part of the feed rolls. Metal, agate or other suitably surfaced bearing means (not shown) may be arranged to press, as fixed or floating bearings, laterally and fiatly on the rolls over their contiguous, tow-bighting portions to assist in their alignment and in preventing the tow from being squeezed out of or otherwise escaping from their nip. In this connection, many of the assembly characteristics and other superficial structural details of apparatus according to the present invention may be in general similarity with certain of the features of the prototype crimping device that is disclosed in U.S. Letters Patent Number 2,311,174 and in the many reproductions and practical variations that have been made in such design.

The cross-section of the stufiing-box B is delineated in Figure 2. Its substantially rectangular configuration, defined by the tow width-accommodating depth D of the box B and its tow thickness-accommodating Width X is designed and dimensioned to most advantageously handle a flat, ribbonlike tow T, of the type that is shown in cross-section in Figure 3. Such a tow bundle may be assembled and shaped in various ways from a plurality of individual filaments F. Many tow forming, drafting and guiding techniques are capable of furnishing such tape-like multiple filament bundles. They are especially easy to obtain when synthetic fibers are being manufactured or processed, or both, in the form of continuous or endless length filaments. Thus, the thickness H of the tow T (the optimum value for which depends to some extent on the precise plurality of individual filaments in the tow) extends in the same direction as the width W of the striding-box B as the tow is being forced into and passed therethrough. The width X of the tow is in similar relative alignment with the depth D of the stuffing-box. In this way, the edges E of the tow T, which traverse and are about coterminous with its thickness, pass through the stuffing-box B contiguous to the side walls 22, 23. The flat sides S of the tow are substantially parallel with the front and rear walls 20, 21. The pitch, or crimps per unit of unextended length in the completely processed and finished product is illustrated on the profile of an individual crimped fiber F, in Figure 4, by the distance N.

In the design and operation of crimpers according to the invention, great care should be taken to ensure that the width W of the stuffing-box B is more than about one and not in excess of about two times the value of the indicated formula. When lesser stuffing-box widths are employed, the flat sides S of the accordion-folded tow in the packed column P will press too hard on and against the side walls of the box causing loss of control and predeterminable effectiveness in the crimping operation and a tendency to frequent jamming of the tow in the apparatus. If greater stuffing-box widths are utilized, the accordion folded packed column P will fold upon itself and enter into an undesirable compound .zigzaggery in the stuffingbox. This results in erratic operations of the apparatus and may produce a crimped product in which there are severely crimped and physically damaged fibers and also in which there may likely be sequential alternate portions of undercrimped or overcrimped gods. Such an erratic and partially cyclic operation as is encountered when overly wide stuifing-boxes are employed may be due to a great pressure build-up within the box as the folded column is folding over upon itself therein, followed by drastic reductions in pressure when such a complex folded, extremely pressured portion of the packed column of tow is finally expelled from the stuffing-box.

The depth of the stuffing-box is commensurate with and may be dimensioned to accommodate a tow of any desired width. A great advantage of the present invention is that exceptionally wide tows may be crimped with great expedience and satisfaction. Thus, besides the half-inch and inch wide flat tows that are often employed and frequently necessitated by limitations of the crimping I apparatus, tows of widths up to four and more inches may be handled with ease. In this connection, the use of a side wall restraining gate facilitates the processing of relatively wider tows and greatly improves the opera tion due to the generally more uniform restraint that it imposes on the packed column in the stuffing-box. When the restraining gate is in or depending from the side wall, the apparatus can be easily threaded up and initially operated with the face plate or front wall open or removed. The actual lacing up of the crimper may thus be laterally accomplished from the front after the tow has been run through the auxiliary guides and the like that are associated with the processing and before closure of the front wall is made. In many of the conventional stufiingbox crimpers, the apparatus must be in complete assembly before it can be threaded up. The tow must thus be started as a more or less cylindrical bundle through the feed rolls. This often causes the pivoted roll to be abnormally displaced during start up and may be responsible for jamming during the threading due to the wide gap that, as a consequence, is left between the wall of the crimper and the widely depositioned roll. As a result, many of the usual crimping apparatus of this variety are not especially useful when tows that have widths much over about two inches are being processed. In addition, a side wall restraining gate greatly simplifies the structure that is involved for'the front wall; generally permitting it to be a plain, one'piece affair.

The most desirable lengths of the stuffing-box and the optimum force to apply to the restraining gate to press it against the packed column of tow are matters that vary with the fineness of pitch in the crimped product being manufactured, the particular fiber that is being crimped, and the specific materials of construction, with given fibers, that are incorporated in the tow-engaging portions of the crimper. Generally, under given conditions, variations in the tow-restricting pressure of the restraining gate vary the pitch that is obtained in the product; the fineness of the crimp being proportional to increases in the restraining pressure. Such pressure, however, is defined largely by the frictional relationships between the material in the tow, as may be affected by its lubricity, moisture or plasticizer content, or both (and possibly one and the same thing) and other recognized factors, and the material of construction that is present in the stuflmg-box. The intrinsic stiffness of a particular fiber and the plural ity of filaments in a given tow also have bearing on the preferred length of stufling-box to be employed and, coupled with the other mentioned aspects, also relate to the optimum restraining force to employ. Thus, it is a practical impossibility to generally predict the pressure to apply for any and all operations. This factor, however, is an easily determinable matter when a given apparatus to be employed on a particular fiber in some relatively constant physical condition is involved under otherwise defined circumstances.

One advantageous embodiment of the invention is shown in Figure 5 of the drawing wherein the apparatus bodiment in sectional side elevation, with the front wall 20 in place, as might be taken along the line 8-8 in Figure 5. In the crimper of Figure 5, the stufiing-box B1, designed to fit the concept of the invention and having a side-wall restraining gate G to bear across the width of the tow, is formed as a straight-through modification with its entrance and exit being in line with the common tangent in the bight of feed rolls 17, 13. The restraining gate G or flapper plate is actuated by the pneumatic cylinder 35 (shown in section) by means of the rod 3 5 which runs through the extending hole 40 in the side wall 22. The length of the flapper plate G, when formed in the most desirable manner, is almost that of the or posite side wall 23. It is so disposed in the assemb'ty that, during operation of the crimper, the stuffing-box is literally an open-ended contraption.

Figures 6 and 7 are fragmentary side views and front elevations, respectively, of the assembled side wall 2?. and restraining gate G which depends pivotally therefrom. They illustrate a suitable means for forming the respective parts and hinging them at their juncture. Thus, the hinge pin 32 is secured in the projecting portion of the side wall which dovetails in the bifurcated upper edge of the gate G which is fastened about the pin. The inner surface at the thus formed hinge should be made as smooth as possible to avoid catching and tearing the packed column of tow in the structure.

In Figure 9 there is represented a preferred configuration for any stuffing-box made according to the invention. It is best flared or relieved toward the exit so that its outlet has a greater cross-sectional area than its inlet. An extent of relief of say, between about two and six degrees, as represented in the drawing by the angle 1) between each of the side walls 22, 23 (with the former being continued by the inner surface of the gate G) and the perpendicular dotted lines is usually suitable and may vary with other factors similar to those mentioned in connection with the optimum pressure to use on the restraining gate.

Figure 10, a view analogous to that employed for Figure 8, indicates the more commonly encountered manner in which the restraining gate or flapper plate G may be provided in the front wall of a stufling-box in a crimper according to the invention. When so provided, the gate presses directly against the thin edge E of the tow packed within the stufling box. Figure 11 illustrates a beneficial construction to utilize for the upper terminating edges of the angular deflecting shoulders at the upper end of the side walls which are positioned closely to (but do not contact) the feed rolls and which actually form the entry throat of the stuffing-box. As shown, the angular deflecting shoulder 25 has a flat surface 45 leading thereto that is disposed to be in a plane forming an obtuse angle 1' with the tangent line q (shown dotted) at the point of proximity between the shoulder 25 and the face of the feed roll. Preferably, the angle r is at least about 105 degrees. Such construction of the terminating edge of the angular deflecting shoulder permits it to have adequate strength to resist being bent by the fibers that are packing into the stufling box so as to avoid scoring or galling of the roll face, as may often occur when thin, weak and Sharper angled blade sections are formed at the upper ends of the side walls.

Another highel advantageous form of stuffing-box B2 is shown in the apparatus that is illustrated in Figure 12. In such embodiment a portion of the length from the entry of the stufiing-box B2 is curvilinear and bent to conform substantially to the curvature of the pivoted feed roll 18. The stuffing-box B2 is offset, as it were, from the bight of the feed rolls. This is accomplished, as is apparent, by displacing the side wall 23 adjacent to and beneath the pivoted roll 18- around the quadrant of the roll and curving the opposite side wall 22 to approximately conform to the roll until it reaches the hinge point with the restraining gate G. This arrangement permits movement of the pivoted roll'18 to be accomplished, if and when necessitated by varying thickness in the tow, while occasioning minimum clearance between the moving or pivoting roll and the upper edge of the side wall. its result, obviously, is to lessen the tendency of the crimper to jam in operation since there is less space in which to catch the tow when large gaps can be avoided between the side walls and the feed rolls. Advantageously, the angular displacement of the upper edge of the side wall 23 about the quadrant of the feed roll 18 is at least about 45 degrees and preferably 80-90 degrees away from and beneath the bight of the rolls. This is illustrated by the angle 0 in Figure 12 between the bight of the feed rolls and the position of the upper, doctor knife-like edge 26 on the side wall 23 against the face of the roll 18.

Further advantage in at least some of the possible forms of this offset arrangement is that it allows the yieldable feed roll .to pivot or move relative to the bight in a laterally linear path, substantially perpendicular to a common tangent through the bight of the feed rolls. This simplifies mounting requirements for the movable roll and neatly avoids the apparatus complexities that are encountered in certain varieties of stuffing-box crimpers wherein arcuately curved side walls extend far up between the rolls toward the bight thereof and the yieldable roll must move in a curvilinear path that, simultaneously, is down and away from the bight of the rolls in order to maintain some semblance of relatively close spacing between the upper knife edge of the side wall and the surface of the roll.

Another significant benefit of an otfset embodiment of stufling-box in accordance with the invention, as accrues with those similar to stuffing-box B2 in the apparatus depicted in Figure 12, is that such modification permits a much greater portion of the force that restricts the pas sage of the packed column of tow through the stufiing-box to be exerted by the restraining gate. This, of course, achieves a closer, more positive and much more advantageous control of the crimping to be secured. The reason for this in an offset type of stutfing-box is tha the influence of frictional forces by the stationary walls of the stuffing-box on the packed column of tow therein is reduced, due to the fact that at least part of the tow confining surface of the stuffing box is formed by the pivotable feed roll 18 whose surface is moving in the same direction as the tow. Some of the frictional forces that would otherwise be present are thus nullified. A wider range of force for purposes of restraint is thus available for application through the restraining gate. In this way, a much greater proportion of the total back-pressure on the packed column of tow in he stutfing box is variable and may be manipulated for achievement of the most desirable results.

The culmination of the advantages possible in an offset type of stuffing-box may be achieved by utilizing an entirely or almost entirely curved stufling-box, similar to that illustrated by the stuffing-box B3 in the apparatus that is schematically portrayed in Figure 13. In this variation of stuffing box in apparatus according to the invention the pivoted feed roll 18 effectively forms all or practically all of an entire side of the crimping zone that is confined within the stufling-box. In such an embodment the wall member 53 is not a functional part of the stufiing box B3 and has nothing to do with deflecting the crimped column towards the outlet of the crimper. Its primary function is to serve as a cleaner for the feed roll 18. To this end, the upper angular deflecting shoulder 26 can actually be employed more in the manner of a conventional doctor knife. Excepting for the roll 9 cleaning function, the member 53 could actually be dispensed with from apparatus similar to that shown in Figure 13 without loss of the desiring crimping action. The opposte side wall 22 of the stufiing-box B3 is curved, somewhat as in the ofiset modification shown in Figure 12, with the restraining gate G that extends the stufiing-box to its actual outlet having an arcuately shaped inner surface and disposed in spaced, approximate conformity to the face of the feed roll 18. The desired cross-sectional configuration of the stufiing box may thus be maintained within the prescribed limits for the entire length of the crimping zone. As is apparent, the frictional influence of a stufling-box patterned after box B3 in Figure 13 is only about half of the frictional influence that is exerted in a stufling box having entirely fixed and stationary confining side walls.

To further illustrate the invention, a crimper based on the herein-disclosed concept would be designed or adjusted to have a stuifing-box width between about 0.17 to 0.34 inch in order to produce a final crimped fiber product having a pitch of about 10 crimps per linear inch from a flat tow having a thickness of about 0.020 inch that would shrink about 25 percent after the crimping operation during its conversion to a dried, finished product. This would be based upon the following calculation, taking the mentioned factors into account and using the indicated formula:

W l(l0.25) The above calculations could be directly applied in the instances when acrylonitrile polymer fibers are being crimped in an aquagel form prior to drying, in which case the value of A would be in accordance with the indicated shrinkage factor. The drying of an acrylonitrile polymer aquagel fiber, say polyacrylonitrile aquagel that contains about 1.5 parts by weight of water to each part by weight of polymer in the hydrated structure, may result in a reduction in length as much as 35 percent upon destruction of the aquagel during its conversion to a dried, finished fiber product. More frequently, however, the shrinkage reduction in length if acrylonitrile polymer aquagel fibers due to their being dried is from 20 to 30 percent. Thus, an aquagel fiber that would shrink about 25 percent on drying to convert it to a final finished crimped product having about crimps per linear unextended inch would, according to the present invention, have about 8 crimps per inch imposed in it while it was in the aquagel fiber form. The same type of considerations apply when the crimper is employed for other types of textile fibers. When acrylonitrile polymer fibers are being crimped while in aquagel form in the practice of the invention, it is generally desirable for the crimping zone in the apparatus that is confined by the stuffing box to be such as to provide 0.5 to 10 seconds of residence time for the fibers in the stuffing box. Oftentimes, at ordinary crimping speeds, this can be accomplished by furnishing about an inch of passage length for the packed column of tow in the stufiing-box for each 0.010 inch of thickness in the tow bundle being crimped.

Apparatus according to the present invention is especially desirable for employment when conducting textile processes in the manner that has been disclosedby Thomas C. Spence, Robert B. Funk and Harry N. Woessner in their copending application for US. Letters Patent having Serial No. 663,693 that was concurrently filed on or about June 5, 1957, covering a Method For Crimping Acrylonitrile Polymer Fibers.

Many changes and modifications can be made in the practice of the present invention without substantially departing from its spirit and scope as is to be construed and interpreted in the light of the hereto appended claims rather than strictly from the foregoing illustrative de scription and specification.

+2 0.020 multiplied by 1 an 2 What is claimed is:

1. Apparatus for crimping textile fibers arrangedin a relatively flat, ribbon-like, multiple filament tow bundle having, as its least dimension, an average thickness of H units of linear measure, said apparatus being adapted to impart an average of N crimps per unextended consistent unit of linear measure in said fiber when it isobtained as a finished crimped product, said apparatus comprising a pair of cooperating driven feed rolls for flatly engaging and forming a bight upon said tow bundle of fibers to continuously force and pack it into the entrance of a stuffing-box associated with the rolls, at least one of said rolls being mounted laterally movable from the bight formed between said rolls to be yieldable to and accommodate passage of varying thicknesses in said tow, said stuffing-box being provided by means defining four walls and having a substantially rectangular cross section, the tow thickness-accommodating width of said stufiing box extending between its side walls, the respective edges of said side walls at the entrance of said stufiing-box terminating adjacent to and extending across the respective faces of said feed rolls so that said tow is forced into said stufling box with its thickness extending in the direction of width between said side walls in said stuffing-box, the edge of each of said side walls that terminate adjacent to a feed roll being shaped to an angular deflecting shoulder having a sharp terminating edge which is formed between the inner surface of the side wall and a fiat surface leading thereto, said flat surface being disposed to be in a plane that forms an obtuse angle of at least about degrees with a tangent line on the face of the feed roll at the pointof proximity between the terminating edge of the side wall and the face of said feed roll, the tow thickness-accommodating width of said stufiing-box being between about one and two times. the value of the expression:

N wherein the symbols H and N are as above defined and A is the shrinkage factor for said fiber between the strandular form in which it is crimped and its form as a final product; and means in said stulfing-box for restraining the passage of packed tow therethrough that has been forced therein by said feed rolls.

2. The apparatus of claim 1, wherein the cross-section of the stufiing-box is relieved away from its entrance by being tapered slightly outwardly in said direction.

3. The apparatus of claim 1, wherein the means for restraining the passage of said packed tow through said stuffing-box is a gate connected to one of the walls of said stuffing-box away from its entrance, said gate being loaded by pressuring means tending to force the gate to restrict the cross-section of said stufiing-box.

4. Apparatus in accordance with that set forth in claim 3, wherein the restraining gate is afiixed hingedly to one of the side walls of said stuffing-box and is disposed to substantially continue the inner surface of the side-wall to which it is affixed.

5. Apparatus in accordance with that set forth in claim 4, wherein the stuffing-box is disposed to lead in a path substantially parallel with a common tangent line between the bight of said feed rolls.

6. Apparatus for crimping textile fibers arranged in a relatively flat, ribbon-like, multiple filament tow bundle having, as its least dimension, an avea'rge thickness of H units of linear measure, said apparatus being adapted to impart an average of N crimps per unextended consistent unit of linear measure in said fiber when it is obtained as a finished crimped product, said apparatus comprising a pair of cooperating driven feed rolls for flatly engaging and forming a bight upon said tow bundle of fibers to continuously force and pack it into the entrance of astufling-box associated with the 11 rolls, only one of said rolls being mounted laterally movable from the bight formed between said rolls to be yieldable to and accommodate passage of varying thicknesses in said tow, said stuffing-box being provided by means defining four walls and having a substantially rectangular cross section, at least the initial portion of said stutfing-box from its entrance leading along a curvilinear path from said entrance, said stuffing-box being olfset from a common tangent line between the bight of said feed rolls in the direction of said movable roll and in approximate configuration with its tow-engaging surface, the side wall of said stuffing-box terminating adjacent tosaid movable feed roll at an angular displacement between about 45 and 90 degrees from the bight of said-rolls, the tow thickness-accommodating width of said stufiing-box extending between its side walls, the respective edges of said side walls at the entrance of said stuffing-box terminating adjacent to and extending across the respective faces of said feed rolls so that said tow is forced into said stutling-box with its thickness extending in the direction of width between said side walls in said stufiing-box, the tow thickness-accommodating width of said stuffing-box being between about one and two times the value of the expression:

N (1-A) wherein the symbols H and N are as above defined and A is the shrinkage factor for said fiber between the strandular form in which it is crimped and its form as a final product; and means in said stuifing-box for restraining the passage of packed tow therethrough that has been forced therein by said feed rolls.

7. Apparatus in accordance with that set forth in claim 6, wherein said angular displacement is from about 80 to 90 degrees.

8. Apparatus for crimping textile fibers arranged in a relatively fiat, ribbon-like, multiple filament tow bundle having, as its least dimension, an average thickness of H units of linear measure, said apparatus being adapted to im art an avera e of.N crim 5 er unextended conand accommodate passage of varying thicknesses in said '1 tow, said stuffing-box being provided by means defining four walls and having a substantially rectangular cross section, substantially all of the stuffing-box leading along a curvilinear path that is in approximate conformation with the tow-engaging surface of said movable feed roll comprising substantially all of one of the side walls of said stuffing-box,- the tow-thickness-accommodating width I of said stuifing-box extending between its side walls, the

respective edges of said side walls at the entrance of said stuifing-box terminating adjacent to and extending across the respective faces of said feed rolls so that said tow is forced into said stufiing-box with its thickness extending in the direction of width between said side walls in said stufiing-box, the tow thickness-accommodating width of said stnffing-box being between about one and two times the value of the expression:

wherein the symbols H and N" are as above defined and A is the shrinkage factor for said fiber between the strandular form in which it is crimped and its form as a final product; and means in said stuffing-box for restraining the passage of packed tow therethrough that has been forced therein by said feed rolls.

9. Apparatus in accordance with that set forth in claim 8, wherein the means for restraining the passage of said packed tow through said stufiing box is a curvilinear gate connected to the side wall of said stuffing-box opposite the movable feed roll away from the entrance of said stuffing-box, said gate being loaded by pressuring means tending to force the gate to restrict the cross-section of said stuffing-box.

10. Process for crimping textile fibers to have an average of N crimps per unit of linear measure as a finished crimped product which comprises forming a plurality of individual filaments of said fiber into a relatively flat, ribbon-like, multiple filament tow bundle having, as its least dimension, an average thickness of H consistent units of linear measure; conveying and forcing said tow bundle into a packed, accordion-folded column of tow in a crimping zone wherein they are restrained under pressure and confined within a chamber having a relatively rectangular cross-section, said tow being conveyed into said crimping zone with its thickness extending substantially parallel with the width of said chamber; withdrawing crimped tow from said crimping zone; and subsequently reducing the length of said fiber by shrinkage factor A for said fiber between the strandular form in which it is crimped and its form as a final product while converting it to a finished fiber product; wherein the tow thickness accommodating width of the rectangular chamber that confines said crimping zone has a value in said units of linear measure between about one and 7 two times the expression:

l N(1A) wherein the symbols are as above defined.

11. The process of claim 10, wherein the fibers are acrylonitrile polymer fibers that are formed into said tow and conveyed and forced into said crimping zone while they are in an aquagel form and wherein they are subsequently reduced in length by drying to destroy the aquagel structure while being converted to a finished crimped fiber product.

12. A process according to that described in claim 11, wherein the residence time of said acrylonitrile polymer aquagel fiber tow during their passage through said crimping zone is between about 0.5 and 10 seconds.

References Cited in the file of this patent UNITED STATES PATENTS 2,686,339 Holt Aug. 17, 1954 2,715,309 Rosenstein et a1. Aug. 16, 1955 2,856,640 Klein Oct. 21, 1958 2,862,279 Fardan, Jr., et a1. Dec. 2, 1958 

